This invention is a method to impart permanent stain resistance to polyamide fibers.
Polyamide fibers are found in a wide variety of commercially important textile materials, including nylon, silk, wool, and leather. It is estimated that 75% of all carpet currently produced in the United States, and 46% of all carpet produced in Europe, is prepared from nylon fiber. Nylon fiber is also used extensively in upholstery and fabric coverings.
One disadvantage in using nylon, as well as other polyamide fibers, as the pile yarn in carpet or as a constituent in fabric is that the fiber is easily stained by many materials. In fact, it has been determined that more carpets are replaced because of staining than because the fibers are worn. The most significant mechanism of action of staining of nylon fiber appears to involve the formation of ionic bonds between protonated terminal amine groups on the polyamide fiber and anionic materials such as acid dyes. Common substances that contain acid dyes include mustard, wine, and soft drinks that contain FD&C red dye No. 40 (such as cherry Kool Aid.RTM.).
The most common approach to increasing the resistance to staining of polyamide fibers has been to treat the fibers with a colorless formaldehyde aromatic condensation polymer that has sulfonate groups on the aromatic rings. The condensation polymers are typically prepared from 4,4'-dihydroxydiphenylsulfone (also referred to as 4,4'-sulfonylbisphenol or DDS), phenyl 4-sulfonic acid, naphthalene sulfonic acid or 2,4-dimethylbenzene sulfonic acid. The sulfonate groups ionically bond to available protonated amino groups in the polyamide fiber, preventing the protonated amino groups from later bonding to commonly used acid dyes.
Examples of methods to impart stain resistance to nylon fibers that include the use of a sulfonated condensation polymer are described in U.S. Pat. No. 4,839,212 to Blythe (disclosing nylon carpet fibers, coated with a sulfonated aromatic condensation polymer, that resist staining by acid dyes at room temperature but are dyeable at elevated temperatures); U.S. Pat. No. 4,501,591 to Ucci, et al. (disclosing the use of sulfonated phenol-formaldehyde condensation polymers in combination with alkali metal silicates to impart stain resistance to nylon fibers); and U.S. Pat. Nos. 4,592,940 and 4,680,212 to Blythe, et al. (disclosing formaldehyde condensation products formed from a mixture of sulfonated dihydroxydiphenylsulfone and phenylsulphonic acid, wherein at least 40% of the repeating units contain an --SO.sub.3 X radical, and at least 40% of the repeating units are dihydroxydiphenylsulfone).
U.S. Pat. No. 4,699,812 to Munk discloses a method for imparting stain resistance to nylon fibers that includes applying a solution of an aliphatic sulfonic acid containing 8 to 24 carbon atoms under acidic conditions.
In a variation of these methods, the sulfonated formaldehyde condensation polymers have been blended with other polymers to increase the effectiveness of stain resistance. For example, U.S. Pat. No. 4,822,373 to Olson discloses a method of imparting stain resistance to nylon fiber that includes applying a mixture of a partially sulfonated novolac resin and a polymethacrylic acid.
European Patent Application No. 88311826.7 filed by E. I. Du Pont Nemours and Company describes stain resistant polyamide fibers prepared by treating the fiber with a hydrolyzed ethylenically unsaturated aromatic maleic anhydride polymer in combination with a sulfonated aromatic condensation polymer.
Although polyamide fibers treated with sulfonated condensation polymers have improved resistance to staining by acid dyes, the resistance is reduced or eliminated after several shampooings, because the sulfonated aromatic condensation polymers are stripped from the fiber. Regardless of the effectiveness of a sulfonated material in imparting stain resistance to polyamides, after several shampooings, the polyamide is just as susceptible to staining as before treatment. This is particularly disadvantageous in a commercial or industrial setting, because of the need for frequent cleaning.
Not only are polyamide fibers easily stained by anionic materials, they are also soiled easily. Fluorochemicals are typically used to reduce the tendency of soil to adhere to the fiber surface, and reduce fiber wettability. Fluorochemicals also provide a physical barrier to the staining material. Examples of commercially available fluorochemical coatings include Scotchgard.RTM. 358 and 352 (Minnesota Mining & Mfg. Co.) and Zepel.RTM. and Teflon.RTM. (E. I. Du Pont Nemours & Co.). Antron Plus.RTM. carpet manufactured by Du Pont contains nylon carpet fibers coated with fluorocarbons. However, fluorochemical coatings alone provide no resistance to staining by acid dyes.
There is a need for a convenient method to impart permanent stain resistance to polyamide fibers that is appropriate for industrial use.
Therefore, it is an object of the present invention to provide a method to impart stain resistance to natural or synthetic polyamide fibers that will not be removed on washing the fiber.
It is another object of the present invention to provide a method for treating natural or synthetic polyamide fiber that is mild enough not to damage other materials attached to the fiber.
It is still another object of the present invention to provide a method to impart permanent stain resistance to nylon carpet and carpet tile for commercial or industrial use.
It is yet another object of the present invention to provide a method to impart permanent stain resistance to natural or synthetic polyamide fabric.
It is a further object of the present invention to provide nylon carpet tile that is permanently stain resistant.